Radio system



C. A. BODDIE Jan. 14, 1930.

RADIO SYSTEM Filed Sept. 13, 1926 Jn. uw

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A TbRNEY WITN ESSES Patented Jan. 14, 1930 UNITED STATES PATENT OFFICE CLARENCE A.. BODDIE, 0F PITTSBURGH, PENNSYLVANIU ASSIGNOR TO 'WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATIONVQF lPENNSYL- VAN IA RADIO SYSTEM Application led September 13, 1926. Serial No. 134,975.

My invention relates to communication systems, and more particularly to communication systems of the type in which high^ frequency oscillations are guided along wire conductors to convey intelligence or to convey 4energy for effecting the operation of electric signalling, controlling and communicating apparatus located at geographically separated points in the system.

One object of my inventionis to provide a system wherein eiiicient communication may be maintained at a plurality of frequencies, one frequency being used for transmission froin a given station vand a .different frequency being employed for reception from distant stations. .I

Another object of my invention 1s to provide in a system of the type described, means whereby duplex communication may be maintained without the necessity of changing the apparatus at any given station from the transmitting to the receiving' state.

Another object of my invention is to provide, in a system of the type described, an efficient antenna for phase-to-phase coupling, such antenna being provided with tuning means whereby it may be rendered simultaneously resonantv to a pluralityl of frequencies.

Still another, and more s eciicobject of my invention, is to provide,in a wired-radio system, an antenna-coupling system comprising only two coupling conductors, intsead of the usual three.

It is now well recognized that, in systems utilizing .power-lines as' guiding channels for high-frequency currents, it is preferable. to use pliase-to-phase coupling insteadof using the'gro'und as the return conductor. It is not necessary, for the purpose of completetly disclosing my invention, to analyze the reasons for the superiority of phase-to-phase coupling, it being suicient to note that it is desirable from the standpoint of efficiency. 'In the past, it has been customary to use two'wires of a three-phase circuit for transmission, the third wire and the ground being utilized for reception. Obviously, this necessitated adding, at each station, three coupling antennae to the poles already supporting the power-lines.

In many instances, it has developed that the line-supporting poles are not sufficiently strong to carry the weight of the additional coupling antennae, and it has become desirable to reduce the number of such antennae to the lowest number compat-ible with eiicient operation.

Obviously, to obtain the most efficient transfer of energy from the transmitting appavratus to the power lines, and from the power lines to the receiving apparatus, itis necessary to employ coupling devices,'tuned to the transmitting frequency on the one hand and to the receiving frequency on the other. By my invention, I eliminate the antenna or coupling condenser formerly employed for reception, by coupling both the receiving and sending apparatus to f the power-lines through two antennae or coupling condensers that are connected together and so tuned, as a whole, to be resonant to -both the transmitting frequency andthe receiving frequency. In addition, I provide an arrangement whereby the transmitting .frequency and the receiving frequency may be interchanged, enabling the operator at any stationfto transmit on the frequency he formerly employedfor receiving and to receiveon the former transmitting frequency.

' The noveli'feaures which I believe' to bei` characteristic of my invention are set forth with' particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, will bestbe understood by reference to the folf lowing description, taken in connection with tlieaccompanying drawings, in which,

' Fig. 1 is adiagrammatic view ofa communicationsystem according to my invention,

ferred form of rnv invention as applied to a single one of the transmitting-receiving station 4 is provided with'ftvglp coupling van- Fig. 2 is a diagrammatic view of a pre-V tennae, 6 and 7, while the station 5 is similarly equipped with two antennae 8 and 9. These antennae are electrostatically, coupled to the power lines, being supported in proximity t creto on poles (not shown).

lAs illustrated in Fig. 2, the antenna 6 is connected, through a variable inductor 11, a

' tuned circuit, comprisingan inductor 12 and a condenser 13, va portion 14. of the secondary of, a radio-frequency coupling-transformer 15, ,the primary of which is connected to the transmitting apparatus (not shown), to' a] grounded conductor 16. The antenna 7 is connected, through a variable inductor 17, a tuned circuit comprising an inductor 18 and a condenser 19, a portion 21 of the secondary of the radio-frequency coupling-transformer 15,A and a coupling inductor 22, to the grounded Avconductor 16.' A circuit, Dcomprising a condenser 23, an inductor I24: and the armature 25 of a wave-change relay 26, is connected in shunt to the coupling inductor 22.

A secondinductor 27 'is so arranged that it may be substituted for the inductor 24, upon actuation of the wave-change relay.

A certain4 capacity exists between the antennae 6 and 7 this capacity being represent- 'ed by a condenser 28.

' by a conductor 35 if desired, for stabilizing purposes. l

The principle of operation of my invention l is based von the fact that a series resonant circuit and a parallel resonant circuit, each separately tuned to the same frequency, will, when connected in series, be resonant to, and have zero reactance at, ltwo separate frequencies. One of these resonant frequencies will lie above the 4frequency to which the separate circuits are tuned, and the other below.

The reactance of a series of resonant circuit is given by the fcrmula 'where equals the reactance, w=2af, Ls= they inductance ,of the circuit, andl Cs==the capacitance associated therewith. The series circuit has zero reactance at the resonant frequency, when l At a lower frequency the capacity reactance predominates, and this reactance is called negative. At a frequency above resonance the inductive reactance is greatest, and the reactance in this'case is called positive.

The reactance of a parallel resonant-'circuit is given by the formula wL X1-a2ac; if the ohmic resistance of the circuit is neglected. Were it not for the resistance of the circuit, the reactance would be lntimte at the rfrequency which makes `the term l mL, v ((L w0$ lw2lp0p ois satisfied by two distinct and separate values of w or, in other words, by two values controlled by the ratio of Ls, the series inductance, to Lp, the parallel inductance. In order, therefore, to obtain an efficient transfer of energy fromthe transmitting set to the power lines at one( frequency and an efficient transfer to the receiving set from the power lines, 'at another and different frequency, it is necessary that the coupling antenna be made resonant, in the manner described above, to these two frequencies.

Referring again to Fig. 1, aseries circuit may be traced to include the condenser 28, the inductors 11 and 17, the radio-frequency coupling-transformer secondaries 1 4 and 21, and the inductor 22. A parallel resonant circuit comprises the inductors 12 and 18 and the condenserslfand 19. The component parts of both theparallel and seriesresonant circuits have been divided equally between the two antennae, in order that the center point therebetween may be grounded, and the current in each antenna may be made equal to that in the other.

The elements of the series and parallel circuits are so chosen that-the two frequencies to Awhich they are resonant, when considered as a whole,"are the transmitting and receiving frequencies to be employed in the operation of the entire system.

The output from the transmitting set is fed into the couplingantennae through the radio-frequency coupling-transformer and causes an oscillatory current in the circuitvv which includes the capacity between antenna 6 and antenna 7 Power is taken from the antennae by theflines 1 and 2 by virtue of the capacity coupling such' lines to each antenna. rIhis capacity is represented by condensers 37 and 38, in Fig. 1.

. Energy received from a distant transmitting station is fed into the receiving set through the inductors 22 and 34, the couplingantenna system being tuned to the receiving frequency, as explained previously.

vIn order-:that'the locally generated transmitting frequency may be prevented from affecting the receiving set,the shunt circuit, including thecondenser. 23 and the inductor 24:, is tuned'to be series'resonantto the transmitting frequency-,andcarries all, or nearly all, of the-transmitting energy circulating Yin the antenna System...l

In addition, the c1rcu1t including the resistance-shouted condenser 31 and the inductor 29 is so arranged that it induces a variable amount of energy at the transmitting frequency, and 180 out of phase therewith into the receiving apparatus 33. This balances out the voltage applied across the receiver due to the ohmic resistance of the shunt-circuit condenser 23 and inductor 24 or inductor 27, as the case may be.

Under certain clrcumstances, it may be desirable to transmit on the frequency no1'- mally used for receiving and to receive on the frequency normally used for transmitting. To accomplish this, a wave-change switch is provided which actuates a relay 26 to connect either of the shunting inductors 24 and 27 A in the circuit. Appropriate changes are made, at the same time, in the tuned antenna circuits, in the adjustment of the receiving set and in the adjustment of the transmitting set. The instrumentalities for accomplishing these changes will be obvious to those skilled in the art, and are, therefore, not specifically shown or described.

The condenser 23 and the inductor 24 are tuned together to the normal transmitting frequency, while the shunt circuit, comprising the condenser 23 and the other inductor 27, is tuned to the normal receiving frequency. It is lthus obvious that, when the appropriate inductor is connected in circuitl by the wave-change relay armature 25, the frequency to which it is tuned will be bypassed and prevented from affecting the receiver 33.

It will thus be apparent that, by my invention, I am enabled to dispense with one of the coupling` antennae or coupling condensers formerly used in duplex transmission over metallic conductors, with no substantial loss in efliciency.

The use of the radio-frequency couplingtransformer to transfer the power from the transmitterl to the tuned circuit has the advantage of materially reducing the interference caused by the radiation of harmonics.

-Although I have described acertain specie form of my invention in detail, and have ointed out the principle upon which it is ased, I do not intend that the language of ,the following claims shall be limited to the of conducting channels, an oscillation generator, an antenna coupled to each channel and fed by said generator, and means whereby said antennae together constitute a single circuit simultaneously resonant to a plurality of frequencies.

2. In a communication system, a plurality of conducting channels, a transmitting set, a receiving set, an antenna coupled to each channel and to each of the transmitting and receiving sets, and 'means whereby said antennae together constitute a single circuit that is resonant simultaneously to a plurality of frequencies.

3. In a communication system, a plurality of conducting channels, an oscillation generator, an oscillation detector", an antenna coupled to each channel, said antennae being so connected together as to constitute a single circuit simultaneously resonant to a plurality of frequencies, and means for coupling said generator and said detector to both of said antennae.

` 4. In a communication system, aplurality of conducting channels, means for generating oscillations, means including a plurality of antennae con stituting a single circuit resonant to a plurality of frequencies for introducing said oscillations into said channels, oscillation detecting means coupled tosaid antenna system, and means including a plurality of reactors, for preventing the generated oscillations from affecting the oscillation detecting means 5. In a communication system, means for transmitting at one frequency, means for receiving at another frequency, said plurality of means mutually including a coupling device tuned simultaneously to both frequencies,

and means whereby the transmitting and rel ceiving frequencies may be interchanged.

6. In a communication system, means vfor transmitting at one frequency, means for receiving at another' frequency, saidplurality of means mutually including a coupling device tuned simultaneously to a plurality of frequencies, and means including an optionally selectable tuned shunt circuit wherebyv the transmitting and receiving frequencies maybe interchanged.

7. In a communication system, a plurality of conductmg channels, an antenna capacitively .coupled to each channel, a connection.

between said antennae including a parallelresonant circuit and a plurality of inductors, the antennae being so disposed that capacitive coupling exists therebetween, whereby the anf said antennae including a parallel-resonant tenna system is resonant to a plurality of frequencies, means for setting up oscillations at one-of said frequencies in said antenna system, a receiving device coupled to one of said inductors, and a circuit series-resonant to said oscillations connected in shunt to the inductor to which said receiving device is coupled. l

8. In a communication system, a plurality of antennae sol disposed as to be capacitively coupled to one another, a connection between circuit and a plurality of inductors, whereby said antennae system is resonant to a plurality vof frequencies, means for introducing oscillationsat one of said frequencies into said antenna system, aI receiving device coupled to one of said inductors for rendering apparent signals received by said antenna system at another of said frequencies, and means' for at Will luy-passing around the inductor to which said receiving device is coupled, oscillations at either of said frequencies.

9. In a communicationsystem, a plurality of conducting channels, a plurality of antennae so disposed as to be capacitively coupled to one another and to said channels, a connection between said antennaeJ including a parallel-resonant circuit and a plurality of inductors, a source of oscillations coupled to said antenna system, a receiving device coupled to said antenna system` and means for preventing said oscillations from adecting said receiving device, said last-named means including alphase-adjusting device.

10. In a communication system, a plurality of conducting channels, a plurality of antennae so disposed as to be capacitively coupled to oneanothez` and to said channels, a connection between said antennae including a parallel-resonant circuit and a plurality of inductors, a source of oscillations coupled to one of said inductors, a receiving device coupled to another of said inductors, a seriesresonant circuit connected in shunt to the inductor to which is coupled said receiving device, for by-passing therearound oscillations at the frequency to which said circuit is tuned, and additional means for preventing said oscillations from affecting said receiving device.

In testimony whereof, I have hereunto subl cribed my nane this 7th-day of September,

CLARENCE A. BODDIE. 

